Published German Patent Application No. 197 12 861 describes a method for regulating the supercharging of an internal combustion engine, in which method a manipulated variable is generated from the deviation between a setpoint charge pressure and the actual charge pressure, the manipulated variable having at least one component supplied by an integral action controller, and a limit value being specified for the integral component which is determined from a base value which is in turn a function of multiple operating parameters of the internal combustion engine and from a correction value superimposed on this limit value. In addition, the correction value is adaptively determined as a function of the rotational speed, with multiple rotational speed ranges being specified. The adapted correction value is incrementally decreased when the deviation is less than a threshold and the integral component is less than the instantaneous limit value. The adapted manipulated variable is incrementally increased when the deviation is greater than zero and the integral component is greater than or equal to the instantaneous limit value.
The manipulated variable for the supercharger is composed of a proportional, a differential, and an integral component. The integral component is limited in the stationary as well as in the dynamic operation of the internal combustion engine. The limit value of the integral component in the dynamic operation is composed of a base value derived from characteristic curves as a function of operating parameters, and a correction value superimposed on the base value. The correction value is adapted as a function of the charge air temperature, the ambient pressure, and the rotational speed of the internal combustion engine.
A method for regulating the charge pressure of an internal combustion engine is also described in published German Patent Application No. 198 12 843 in which a manipulated variable for an actuator is generated from the deviation between a setpoint charge pressure and the actual charge pressure, the actuator acting on the exhaust gas stream supplied via the turbine of an exhaust gas turbocharger. The manipulated variable, or one or more other quantities forming the manipulated variable, in a characteristic map is (are) transformed into values such that at least approximately linear relationship exists between the manipulated variable and the controlled variable—the charge pressure—after the transformation.
The resulting characteristic of the charge pressure regulating system may be described by a straight line and an offset in the form of the base charge pressure. This base charge pressure is an undesired characteristic of the waste gate actuator common in a gasoline engine, for example, caused by the supply of excess pressure from the charge pressure. The base charge pressure is the lowest control threshold (0% pulse duty factor) of the charge pressure regulation for any given internal combustion engine, for example spark-ignition and diesel engines, and is modeled within the engine controller.
Previously, the adaptation values for the limit value have been formed in the form of an offset value on the pulse duty factor level. This adaptation offset is stored by filing in cells which are addressable via the engine rotational speed.
The task of the limitation of the integral component includes, among others, the prevention of controller-induced over-swing in the charge pressure. To this end, an applied manipulated variable requirement is determined as a function of the engine rotational speed and the relative setpoint charge pressure, which is equal to the absolute charge pressure minus the base charge pressure. In addition to the referenced adaptive correction, this pulse duty value is corrected using charge air temperature and warm-up interventions.
In this method, it is problematic that for charge pressure setpoint values below the base charge pressure the above-referenced adaptation offset is constantly output, which for strongly positive adaptation values may result in an excessively high upper limit for the integral component, with corresponding over-swings in the charge pressure.